This is apache 2.2.14 on SLES9.
Out of nowhere (i.e. it had been working fine for ages) I am seeing apache2 suddenly start using 100% of the CPU at startup, and never completing startup. Nothing is getting written to /var/log/error_log (when it did back when things were OK). ps only shows the main httpd process and not any of the spawned threads. When things were OK, it would show the spawned threads.
So it appears httpd is going into some sort of infinite loop right at startup and isn't even completing startup. It's not an issue of being overloaded by connections -- this happens even when nothing is trying to contact it.
The config files haven't changed (or at least they haven't changed in a way that changed their last-modified time).
I've tried added -e debug -E /var/log/apache2/startup_info to the command line, but nothing is put in the file.
Any ideas what could be happening?
It turns out the problem was that apache's SSL session cache file got corrupted. Once we stopped apache again and deleted the file everything was fine again.